This invention relates to the need for developing new plastic materials that can be used in applications where biodegradability, compostability or biocompatibility are among primary desirable features of such applications. There have been many attempts to make degradable articles. However, because of costs, the difficulty in processing, and end-use properties, there has been little commercial success. Many compositions that have excellent degradability have only limited processability. Conversely, compositions which are more easily processable have reduced degradability.
An example of a molded or extruded article that accumulates in the environment is a plastic tampon applicator. Paper tampon applicators are considered environmentally friendly in that they readily disintegrate in a sewage system and/or can be disposed of through aerobic, anaerobic, or natural degradation processes. However, paper tampon articles are not most favored among females due to pledget insertion difficulties associated with their use. Certain female consumers prefer plastic tampon applicators because the plastic applicators are easier to insert, however, most plastic tampon applicators are made from polymeric materials that are not biodegradable and that do not readily soften or break-up into smaller fragments for decomposition in a sewage system, resulting in increased environmental concerns.
An applicator made from water soluble polymers such as polyvinyl alcohol suffers from moisture sensitivity, stability, odor, or stickiness. Further, a plastic tampon applicator constructed from water soluble polymers, such as polyvinyl alcohol and polyethylene oxide, does not provide enough in-use integrity during insertion and tends to stick to sewer pipes after flushing which can lead to clogging of toilet systems and/or drain pipes.
Polyhydroxyalkanoates (PHAs) are thermoplastic polymers desirable for use in molded or extruded articles particularly due to their biodegradability. U.S. Pat. No. 5,498,692, issued Mar. 12, 1996 to Noda, and U.S. Pat. No. 5,502,116, issued Mar. 26, 1996 to Noda, relate to molded articles comprising PHAs. Molded articles from such PHAs remain substantially tacky after they are cooled down from the melt, and remain as such until sufficient crystallinity sets in, particularly with PHA copolymers levels above 10 wt %. Residual tack typically can lead to material sticking to itself or to the processing equipment, or both, and thereby can restrict the speed at which a polymeric product is produced or prevent the product from being collected in a form of suitable quality. A poly(3-hydroxybutyrate-co-3-hydroxyvalerate) product commercialized under the name BIOPOL® suffers from hardness, brittleness, and from having very slow crystallization kinetics. Similarly, U.S. Pat. No. 5,292,860 to Shiotani lacks teachings regarding compositions having short cycle times in the manufacturing process for molded or extruded articles.
Consequently, there is a need for melt processable compositions of environmentally degradable polymers for use in molded or extruded articles where the polymers have economically viable annealing cycle times. Moreover, the compositions should be suitable for use in conventional processing equipment, and resultant molded or extruded articles should meet consumer acceptability for their structural integrity and aesthetic characteristics of smoothness, flexibility, reduced stickiness, stability, and the like.